Java EE (Java Enterprise Edition) General Discussion

Hi,
I am currently working on a Portal project (we're using IBM websphere portal server) which requires conversion of a set of data from the oracle DB into an excel file and pass this to a jsp file providing an option to the user to either view the excel sheet or dowload and save it (the normal windows popup asking the user if (s)he wants to open the file or save it on the disk). The front end is Netscape 7.0 browser.
I've accomplished the first part of excel file creation, but am unable to send the excel file from server to the client side (ie to the browser).
The code
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response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "filename=mf.xls" );
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which works perfectly fine when used as a standalone to popup an excel sheet in tomcat server, fails to accomplish anything in the Websphere Portal Server Environment.
Can anyone who've faced and overcome such a problem throw some light on this.
Thanks in anticipation,
regards,
Kashyap.